The time variations of signals $A, B$ and $C$ are shown below. Choose the correct statement.

In which of the following cases is the junction diode $NOT$ in reverse bias?

The voltage gain of the following amplifier is

The voltage gains of two amplifiers connected in series are $8$ and $12.5$. If the voltage of the input signal is $200 \mu V$, then the voltage of the output signal is

Given below are two statements:
Statement $I$: Photovoltaic devices can convert optical radiation into electricity.
Statement $II$: Zener diode is designed to operate under reverse bias in the breakdown region.
In the light of the above statements,choose the most appropriate answer from the options given below:

The energy of a photon of sodium light $(\lambda = 589 \text{ nm})$ is equal to the band gap of a semiconductor. Find the minimum energy $E$ in $eV$ required to create an electron-hole pair.